The Internet is growing in popularity, and more and more people are conducting business over the Internet, advertising their products and services by generating and sending electronic mass mailings. These electronic messages (emails) are usually unsolicited and regarded as nuisances by the recipients because they occupy much of the storage space needed for necessary and important data processing. For example, a mail server may have to reject accepting an important and/or desired email when its storage capacity is filled to the maximum with unwanted emails containing advertisements. Moreover, thin client systems such as set top boxes, PDA's, network computers, and pagers all have limited storage capacity. Unwanted emails in any one of such systems can tie up a finite resource for the user. In addition, a typical user wastes time by downloading voluminous but useless advertisement information. These unwanted emails are commonly referred to as spam.
Presently, there are products that are capable of filtering out unwanted messages. For example, a spam block method exists which keeps an index list of all spam agents (i.e., companies that generate mass unsolicited emails), and provides means to block any email sent from a company on the list.
Another “junk mail” filter currently available employs filters which are based on predefined words and patterns as mentioned above. An incoming mail is designated as an unwanted mail if the subject contains a known spam pattern.
However, as spam filtering grows in sophistication, so do the techniques of spammers in avoiding the filters. Examples of tactics incorporated by a recent generation of spammers include randomization, origin concealment, and filter evasion using HTML.
Another tactic spammers use to avoid filters is soliciting recipients to perform additional actions beyond reading the incoming email. An example of one such method is providing a Uniform Resource Locator (URL) in the body of the email that points to a Web site.
Spammers often disguise the URL to make the URL look legitimate. The disguised URLs, purporting to originate from legitimate organizations, may then be used to entice recipients to provide private and financial information.